The present invention relates to presses, more particularly powder compacting presses, provided with a reciprocable ram disposed above the press die supporting bed and to a method for compacting powder material by means thereof. More specifically, the invention relates to an improved mechanism for actuating the ram of a press and consisting of a combination of a mechanical toggle mechanism and fluid operated mechanism.
The present invention is an improvement on the presses disclosed in U.S. Pat. Nos. 3,826,599 and 4,166,716, assigned to the same assignee as the present invention. The presses disclosed in the aforesaid patents are provided with a ram disposed above the press bed in which is mounted a powder compacting apparatus comprising a die plate having one or a plurality of die cavities disposed therein. A punch is reciprocably disposed in each die bore and is actuated by the drive mechanism of the press by means, for example, of a power-driven camshaft and an appropriate cam follower driving the punch holder. A ram is reciprocably disposed above the press bed, therefore above the die plate, and is reciprocated in timed relationship with the reciprocation of the punch holder by an appropriate cam, cam follower, lever and toggle mechanism. A set of punches, each adapted to co-operate with a punch disposed in a die bore, can be mounted on the end of the ram and, or in addition, the ram, in its fully extended position, may be used to clamp over the die plate an anvil adapted to close the die cavity or cavities, and having a face overlapping the die cavity opening or openings, against which the powder material disposed in the die cavities is compacted by the punch or punches held in the die bore or bores. The anvil, together with a powder material dispenser and a finished part pick-up mechanism, is mounted on the end of a positioning arm, such as to be arcuately or linearly displaced and positioned over the die cavities in timed relationship with the die cavity filling step, the compacting step and the finished article ejection step. Such an arrangement of elements is described in the aforesaid patents and in U.S. Pat. Nos. 3,561,054 and 3,574,892, for example, of common ownership herewith.
The present invention is an improvement on the ram operating toggle mechanism disclosed in U.S. Pat. No. 4,166,716 and application Ser. No. 183,011, now U.S. Pat. No. 4,302,412, issued Nov. 24, 1981. In the aforementioned patents there is disclosed a mechanism providing a floating fluid pressure displaceable anchoring and pivoting point for the ram toggle mechanism, such that the ram may additionally be longitudinally displaced as a result of the reciprocation of the anchoring and pivoting point. Adjustable limit abutments are provided for the fluid actuated reciprocating anchoring and pivot point of the toggle mechanism, such that the stroke provided by the fluid actuated mechanism may be precisely determined, together with the extreme positions of the reciprocating member.
An arrangement is thus provided for compound reciprocation of a press ram and for precisely determining the extreme dwell positions of the ram. By thus providing a compound stroke of the press ram, part of the stroke being mechanically effected by a toggle mechanism and part of the stroke being pneumatically or hydraulically effected, the motion increments being either consecutive or simultaneous, according to the appropriate timing of the beginning and end of the two separately controlled motions, diverse results can be achieved.
One such result is that, in arrangements where the end of the arm is provided with a clamping mechanism for the positioner anvil, by proper timing of the clamping step pneumatic or hydraulic pressure may be exerted on the anvil prior to final mechanical clamping provided by the toggle mechanism, so that the clamping pressure applied on the anvil may be more progressive and is effected with a cushioning effect.
Another result is that, in structures comprising punches mounted on the end of the ram, such punches being adapted to penetrate into the die cavities and compact the material therein in the die bore between the end face of the ram mounted punches and the end face of opposedly reciprocating punches disposed in the die bore, compacting of the powder material can be effected in a more progressive manner as compared to methods using a mechanically actuated upper punch, and the density of the finished part is greatly improved as compared to the density of parts compacted under more conventional methods.
Because the dwell position of the ram and the force exerted by the ram are not the same when the ram is used for clamping an anvil over the die cavity or cavities and when the ram carries punches which are introduced into the die cavities for compacting the powder material between opposite punches, different cam contours are required for the cam actuating the toggle mechanism disclosed in U.S. Pat. Nos. 4,166,716 and 4,302,412, according to whether the press is used in an anvil press mode or an opposed punch mode. As the cam operating the toggle mechanism and the cam operating the lower punches are mounted on a common camshaft installed within the housing of the press apparatus below the table, changing cams is a lengthy and delicate operation resulting in substantial downtime in the operation of the press apparatus.